Muffler with plural side branch chambers



Feb. 27, 1951 E. D. LATULlPFE MUFFLER WITH PLURAL SIDE BRANCH CHAMBERSFiled July 20, 1949 2 Sheets-Sheet l 500 ZZLAruL/PPA' BY 1/(w m wjwwwwmw Feb. 27, 1951 E. D. LATULIPPE MUFFLER wrm PLURAL SIDE BRANCHCHAMBERS Filed July 20. 1949 2 Sheets-Sheet 2 INVEN'I'OR. 00) fl. Z A704 IPPE BY aL Patented Feb. 27, 1951 MUFFLER WITH PLUR-AL SIDE BRANCHCHAMBERS Eddy D. Latulippe, Englewood, N. J., assignor to Acre-SonicCorp., New York, N. Y., a corporation of New York Application July 20,1949, Serial No. 105,686

9 Claims.

This invention relates to exhaust mufiiers of the type disclosed by theE. D. Latulippe Patent No. 2,158,030 issued May 9, 1939. This type maybe used to muffle any exhaust creating an acoustical disturbance. It isparticularly adapted for application to aircraft having enginesproducing exhausts which it is desirable to muilie to make theircharacteristic noise less disturbing. This type may be produced in alight-weight form producing relatively littleback pressure whileeffectively muffling.

One of the objects of the present invention is to improve on this typeof muffler to produce a light-weight muffler that muffles even moreeffectively with even less back pressure. When back pressure is exertedagainst an exhaust from an engine the engine cannot operate at itsmaximum power. It is undesirable to decrease the maximum power of anaircraft engine. Another object is to improve on this type of muiiler toproduce a mullier that may be more easily manufactured and which isconstructed so its parts are less likely to shake loose during the heavyvibration and generally severe service conditions encountered inaircraft applications. Other objects may be inferred from the following.

A specific example of a muffler constructed in accordance-with thepresent invention is illustrated by the accompanying drawings. anddescribed hereinbelow for the purpose of disclosing the principles andoperation of this invention. No unusual manufacturing problems areinvolved and anyone skilled in the art who knows the principles andoperation of the invention may construct this exemplary muffler. Suchfamiliarity will permit changes in the specific details shown and willenablethe production of various modifications. One suggestivemodification is illustrated. by the drawings and described herein.

In these drawings Fig. 1 is a side elevation of the mufiler;

Fig. 2 is a longitudinal, vertical section with the parts clarified by ascale enlargement which requires the mufiier to be broken because ofspace Fig. '7 is a view similar to Fig. 2, but is on a relativelyenlarged scale and shows the tail piece in modified form;

.Fig. 8 is an end view of Fig. 7, and

Fig; 9 is a vertical transverse cross section taken on the line 99 inFig. 7.

Referring to Fig. l the mufiler has an elongated outer casing in theform of a cylindrical tube. The inlet end of this casing I has atapering" inlet chamber 2, and the outlet end of the casing I has atapering outlet chamber 3. The exhaust pipe 4 connects with the inletchamber 2 while as part of the muflier to tail piece 5 extendsbackwardly and downwardly at an angle from the outlet chamber 3. Theexhaust pipe 4 is shown with an air inlet pipe 6 provided with an airfunnel I so the movement of the aircraft drives air through the pipe 6into the exhaust pipe 4 to keep enough air in the exhaust and mufilersystem to prevent an explosion hazard in the event the aircraft enginemisfires and fills the system with unburnt fuel.

It is to be assumed that the mufiier is applied to an aircraft. Thedevice is long and relatively slender and so has little wind resistancewhen installed on the outside of the aircraft where it is exposed.

The mufilers internal construction is shown by Fig. 2. In addition tothe outer casing I the mullier has an elongated inner casing 8. Theouter casing I and the inner casing 8 are mutually spaced and arerespectively constructed and mutually arranged to conduct the exhaustbetween the casings I and 8 and-inside of the inner casing 8. This innercasing 3 is also shown as a cylindrical tube and it is concentricallyarranged inside the outer casing I. The casing 8 is of smaller diameterthan the casing I so its outside is mutually spaced from the inside ofthe casing I to provide a tube-likespace extending longitudinally of themuffler. The inside of the inner casing 8 provides anotherlongitudinally extending space.

The outer casing I has superimposed and mutually spaced outer and innerwalls. The outer wall Ia is substantially gas-tight and may comprise asheet metal tube. It joins with the chambers 2 and 3 in a gas-tightmanner. The inlet chamber 2 is connected with the exhaust pipe 4 in agas-tight manner and the tail piece 5 is connected with the outletchamber 3 in a gastight'manner. All of these parts of the muiiler may bemade from sheet metal that is free from openings.

The outer casings inner wall I b is perforated throughout its entireextent. It may comprise a sheet metal wall having sufficientperforations to give it the characteristic of a screen. The ends of thisinner wall lb have outwardly projecting annular flanges lc by which itis connected with the outer wall la of this outer casing l.

The inner casing 8 has superimposed and mutually spaced outer and innerperforated walls Ba which are similar to the wall lb of the outercasing. The inner casing also has a central substantially gas-tight wall8b which is substantially like the outer wall la of the outer casing I.Where reference is here made to walls being substantially alike it is tobe understood that different diameters are involved and that the endsare slightly modified in the respective instances. Thus the ends of theperforated walls 8a of the inner casing are joined together at theirfront ends by inner and outer rings H which have flanges connecting withthese walls 8a and which taper inwardly to provide flanges which areinterconnected by being fastened to the gas-tight wall 8b which has itsend sandwiched between them. At the outlet end of the device the outerone of the perforated walls 8a is tapered inwardly and fastened to theinner one of the walls 8a with the gas-tight central wall 8b buttedagainst the tapering end of the outer perforated wall.

In Fig. 2 the perforated insides of the inner walls of the outer andinner casings respectively are shown perforated only in thecross-sectioned portions. This is done to avoid confusion which resultswhen the holes are shown throughout the curving halves illustrated inelevation. Fig. l is provided to clarify the construction, and in thisthe perforations in the walls lb are marked Id and those in the walls 8aof the inner casing are marked 80. All of the perforations ld in theelevation portion of this figure are not shown but a few are indicatedto show their distribution. In all cases the perforations are relativelysmall and there are a relatively large number of them, the walls beingcompletely filled with the perforations in each instance.

As shown particularly well by Fig. 3, the inner casing is positionedinside the outer casing by the use of short channel sections l2 havingtheir webs radially arranged and their flanges fastened to the wall lband the outer one of the walls 8a respectively. Sufiicient of thesechannel sections are used to secure rigidly and they are shown only atthe ends of the two casings.

Fig. 3 also shows that the various walls are formed by cylindricallybending metal sheets and overlapping and fastening their ends. Buttjoints could also be used if the joints are made adequately permanent.

The tail piece 5 of the device is shown in maximum detail by Figs. 2 and5. This tail piece includes superimposed, gradually flattening tailconduits 5a and 5b which extend backwardly from the chamber 3 in agas-tight manner as previously explained. Conduit 5b connects with theinside of the inner casing 8 through an inner short casing 3a thatextends through the outer casing 3b of the chamber 3 as a short tubularcylinder part having its inner end fastened to the tapering wall of theouter one of the walls 8a of the inner casing. Thus the chamber 3comprises the outer short casing 3b and the inner short casing 3a. Thislatter casing 311 is provided with a plurality of partial punches 30which are formed as inwardly projecting scoops pointing in the directionthe exhaust comes from the inner casing. This inner short casing 3apositions the inner end of the conduit 5b within the tail piece and theouter end of the conduit 5b is rigidly positioned therein by a pluralityof short channel sections 50. These sections are arranged with theirwebs transversely between the outer flat end of the outer tail conduit5a with their flanges fastened to its insides. These sections have slots5d receiving the flattened end of the inner tail conduit 5b. The partsare assembled in a rigid manner.

The outlet chamber 3 and the tail piece 5 follow the general arrangementof the comparable parts disclosed by the mentioned Latulippe patent.They differ from it in that a larger number of the openings or scoops 3care used and in that these openings are arranged directly inside of theoutlet chamber 3b rather than farther back in the tail piece. The tailpiece is also shown angling downwardly because this is generally abetter arrangement for many aircraft installations.

As shown in Fig. 2 the spacing between the walls of the respectivecasings is considerably less than the spacing between the two casingsproper. Sound absorbent material lla is positioned between the mutuallyopposed'surfaces of the gas tight walls and the perforated wallsrespectively. Thus this sound absorbent material is positioned betweenthe walls la and lb and between the walls 841 and 8b. The absorbentmaterial may comprise stainless steel wool or other refractory fibrousmaterial capable of resisting the vibration. This material is packedrelatively compactly between the respective walls. The material shouldbe acoustically absorbent respecting at least the dominant frequenciesof the exhausts vibration.

With the muffler connected with the exhaust pipe and with the lattercarrying the exhaust creating the disturbing noise the operation of themufiler is as follows.

The exhaust gases enter the inlet chamber 2 and are thereby connectedwith both the space between the two casings and the space inside theinner casing. The chamber 2 functions to equalize the pressure betweenthese two spaces. The exhaust travels through both spaces and into theoutlet chamber 3 through which it passes to exit through the tail piece5. This tail piece functions to impede the flow of the exhaust gasesfrom the outlet chamber to provide a very slight back pressure whichslightly increases the normal pressure of the exhaust traveling throughthe casings of the muffler. The openings 3c in the short inner casing 3aof the outlet chamber 3 also interconnect the spaces between the casingsand inside the inner casing to assure pressure equalizationtherebetween. The flattening of the respective tail piece conduitsshould be adequate to provide this slight back pressure effect, but notsumcient to impede the exhaust so much as to materially affect the poweroutput of the engine producing the exhaust.

Since the pressures in the two spaces provided by the two casings arethe same the exhaust gases tend to travel uniformly through both spaces.As the exhaust gases travel through the spaces the exhaust gases areconfined by the double walled construction shown and described. Thegases tend to penetrate the perforated wall so that the sound absorbentmaterial l2 functions as a sound absorbent wall carrying the exhaustgases. As

a result the acoustical energy is effectively mufiled out by absorption.This is done without abrupt accede- 1 5 changes of theaflow-ing'direction: of i the exhaust ases or' in any otheryway-impeding theexhaust gasesflow-materiallwte result :in high' back pressure;

The -murder: illustrated is. relatively small. In the case of largermu'fll'ers intendedfor larger engines the-number of multiple-walledcasings may be increased to prov-idemore efiective sound absorption fromthe traveling exhaust gases;

The slight tape-r of the exhaust chamber 312' is insome instances byitself sufficient-to impede the exhaust flowing from the' muffiertoasufficient extent to materially increase thesoundabsorption properties;Where-adequatesound absorption is provided in thisfashionthe tail piece5 may be eliminated.- The tail piecemay also be eliminated in caseswhere themufii'er is made longer to maintain theexhaust gases in-contact with the sound absorbent material for a longer period of timethan-in thecase ofthe shorter muffler illustrated.

Since the exhaust is simply carried straight through the muffler theparts may be'made very light in weight by'using relatively thin-gaugedsheet metal suchas thin stainless steel. Any pulsations'inthe exhaustare-rapidly damped out by the sound absorbent material l2 so that themuffler is not subjected to=material vibration due to the exhaust;

In the modification shown by Figs. 7" through 9' a straightcylindricaloutl'et chamber 14 is substituted' for the taperedchamber-Ii'ofthe mufiler assembly shown-by Figs. 1" through 5; This per-'- forms"all the functions-previously described. The various walls of the, innercasingaresomewhat differently arranged but this diiference is relativelyslight andneed not be described since-it is apparent from the drawings.

The modified tailpiece I5= has an outer casing shaped somewhat like an'egg-and internally provided with a tear drop shell 16 positioned withits large endpointingtowardstheflow of exhaust gases andwith its outsidespacedfrom the inside of the shell [5 by struts ll turned edgewise'tothe flowing exhaust-gases. The casing-"and shell correspond generally incontour.

With this modified arrangementthe tear "drop shell I 6 provides a slightflow impedancetobuild upthe'slightback pressure back inthe mainportionof the mufl'ler. directly impinged by the exhaust gases leaving theinnercasing-its'general shape is such that it does not have to: provide muchreaction to these gases; The shells' shape makes it inherently rigid.Furthermore it isreceiving the exhaust gases after the vibrationenergyhas been largely removed.by-being absorbed by the sound absorbingmaterial between the multiple; walls of the various casings:

It is to be noted that the construction" is' such that'theexhaust gasescannotienterbetween the various walls of the respective casings l' and'8through any spaces between their endedges. The effect is substantiallythat Qf'cOnduQtingthe exhaust gases through a plurality-of straightsoundabsorbent passageway walls. with the. exhaust uniformly distributed.throughout the various passageways without any localized pressurenonuniformities. The uniform distribution of the pressure throughouttheentiredeyice not only affects maximum sound. dampening. or. muffling buthas the further. adivantagefofj preventing .the formation of localized.hotspots in' the. muffler construction.

The acoustical absorbent. material. permits Althou h the shell IE is rsome-penetration by the exhaust; The-acoustical energy'in the absorbedexhaust is reflectedlback and forth between the. respective casing wallsand thus: damped out. Thiseflect. is; obtained when the. sound absorbentmaterial is eliminated.

When using the material thetefiect increases the sound, absorptionefficiency.

Assshown by Fig. 7 the tail of the tear drop shell [6. is: longv andprojectstwell beyond the back end of the outer: casing I5. The outletend of thecasing [5 has substantially the. same inside diameter. as thatof. the inlet chamber 2 of the muffler where it connectswith the exhaustpipe 4. The. contours of the casing l5 and shell IS follow each other asmuch aspossible with the foregoing qualifications. Thisconstructionproducesa jet eiiject providing thrustfor pushing the aircraft.

Iclaim:

1. An exhaust muffler including mutually spaced outer andv innerelongated casings constructed and arranged to conduct the exhausttherethroughbetween said casings and inside said inner casing, saidouter casing having superimposed andimutually spaced outer and innerwalls with: said outer wall substantially gas-tight and said inner wallperforated, and said inner casing having superimposed and mutuallyspaced outer and inner perforated: walls anda central substantiallygas-tight wall interposed therebetween.

2. An exhaust muii'ler including mutually spaced outer and innerelongated casings con structed and. arranged to conductthe, exhausttherethrough. betweenv said. casings and inside saidlinner casing, saidouter casing having superimposedand mutually spaced outer. and innerwalls with said outer'wallsubstantially gas-tight and said inner wallperforated, and said inner casing having superimposed and mutuallyspaced outer and inner perforated walls and a central substantiallygas-tightwall interposed therebetween, sound-absorbent material beingpositioned between the mutually opposed surfaces of said substantiallygas-tight walls and said perforated walls respectively.

3.. An exhaust muffler including mutually spaced outer andinnerelongated casings. constructed and arranged to. conduct the exhausttherethrough between said casings-and-inside said inner casing, saidouter casing havingsuperimposed and mutually spacedouter and-inner wallswith said outer wall substantially-gas-tight and said inner wallperforated, and said inner casing having superimposed and mutuallyspace-d outer and innerperforated. walls and a central substantiallygas-tightwall interposed therebetween, said casings having aninlet'chamber at their exhaust-inlet endswith the latter and saidchamberconstructed and arranged to interconnect'the respectiveinsidesofsaid casings and to introduce the exhaust thereto, and said casingshaving an outlet chamber at their exhaust-outlet-ends with the latterandsaid outlet chamber constructed and arrangedto interconnect theirrespective insidtsandto carry the. exhausttherefrom...

4.. An exhaust muffier including mutually spaced outer andinnerelongated casings con structed and arranged to conduct. the exhausttherethrough between said casings and inside inner. casing, said outercasing having superimposed. and: mutually spaced outer and inner. wallswith said outer Walls substantially gas-tight and said inner wallperforated, and said inner casing hayingsuperimposed and mutually spacedouter and inner perforated walls and a central substantially gas-tightwall interposed therebetween, said casings having an inlet chamber attheir exhaust-inlet ends with the latter and said chamber constructedand arranged to interconnect the respective insides of said casings andto introduce the exhaust thereto, and said casings having an outletchamber at their exhaust-outlet ends with the latter and said outletchamber constructed and arranged to interconnect their respectiveinsides and to carry the exhaust therefrom, sound absorbent materialbeing positioned between the mutually opposed surfaces of saidsubstantially gas-tight Walls and said perforated walls respectively.

5. An exhaust muffler including mutually spaced outer and innerelongated casings constructed and arranged to conduct the exhausttherethrough between said casings and inside said inner casing, saidouter casing having superimposed and mutually spaced outer and innerwalls with said outer Wall substantially gas-tight and said inner wallperforated, and said inner casing having superimposed and mutuallyspaced outer and inner perforated walls and a central substantiallygas-tight wall interposed therebetween, said casings having an inletchamber at their exhaust-inlet ends with the latter and said chamberconstructed and arranged to interconnect the respective insides of saidcasings and to introduce the exhaust thereto, and said casings having anoutlet chamber at their exhaustoutlet ends with the latter and saidoutlet chamber constructed and arranged to interconnect their respectiveinside and to carry the exhaust therefrom, said outlet chamberconnecting with means for at least slightly impeding the exhaust flowtherefrom.

6. An exhaust muffler including mutually spaced outer and innerelongated casings constructed and arranged to conduct the exhausttherethrough between said casings and inside said inner casing, saidouter casing having superimposed and mutually spaced outer and innerwalls with said outer wall substantially gas-tight and said inner wallperforated, and said inner casing having superimposed and mutuallyspaced outer and inner perforated walls and a central substantiallygas-tight wall interposed therebetween, said casings having an inletchamber at their exhaust-inlet ends with the latter and said chamberconstructed and arranged to interconnect the respective insides of saidcasings and to introduce the exhaust thereto, and said casings having anoutlet chamber at their exhaust-outlet ends with the latter and saidoutlet chamber constructed and arranged to interconnect their respectiveinsides and to carry the exhaust therefrom, sound absorbent materialbeing positioned between the mutually opposed surfaces of saidsubstantially gas-tight walls and said perforated walls respectively,said outlet chamber connecting with means for at least slightly impedingthe exhaust flow therefrom.

'7. An exhaust mufiler including mutually spaced outer and innerelongated casings constructed and arranged to conduct the-exhausttherethrough between said casings and inside said inner casing, saidouter casing having superimposed and mutually spaced outer and innerwalls with said outer wall substantially gastight and said inner wallperforated, and said inner casing having superimposed and mutuallyspaced outer and inner perforated walls and a central substantiallygas-tight wall interposed therebetween, said casings having an inletchamber at their exhaust-inlet ends with the latter and said chamberconstructed and arranged to interconnect the respective insides of saidcasings and to introduce the exhaust thereto, and said casings having anoutlet chamber at their exhaust-outlet ends with the latter and saidoutlet chamber constructed and arranged to interconnect their respectiveinsides and to carry the exhaust therefrom, sound absorbent materialbeing positioned betwen the mutually opposed surfaces of saidsubstantially gas-tight walls and said perforated walls respectively,said outlet chamber connecting with means for at least slightly impedingthe exhaust flow therefrom, said outlet chamber including asubstantially gastight outer short casing extending from said outerelongated casing and an inner short casing having gas ports andpositioned inside and spaced from said outer casing and extending fromsaid inner elongated casing. A

8. An exhaust muffler including mutually spaced outer and innerelongated casings constructed and arranged to conduct the exhausttherethrough between said casings and inside said inner casing, saidouter casing having superimposed and mutually spaced outer and innerwalls with said wall substantially gas-tight and said inner wallperforated, and said inner casing having superimposed and mutuallyspaced outer and inner perforated walls and a central substantiallygas-tight wall interposed therebetween, said casings having an inletchamber at their exhaust-inlet ends with the latter and said chamberconstructed and arranged to interconnect the respective insides of saidcasings and to introduce the exhaust thereto, and said casings having anoutlet chamber at their exhaust-outlet ends with the latter and saidoutlet chamber constructed and arranged to interconnect their respectiveinsides and to carry the exhaust therefrom, sound absorbent materialbeing positioned between th mutually opposed surfaces of saidsubstantialy gas-tight walls and said perforated walls respectively,said outlet chamber connecting with means for at least slightly impedingthe exhaust flow therefrom, said outlet chamber including asubstantially gas-tight outer short casing extending from said outerelongated casing and an inner short casing having gas ports andpositioned inside and spaced from said outer short casing and extendingfrom said inner elongated casing, said means including superimposedgradually flattening tail conduits respectively extending from saidouter and inner short casmgs.

9. An exhaust muffler including mutually spaced outer and innerelongated casings constructed and arranged to conduct the exhausttherethrough betwen said casings and inside said inner casing, saidouter casing having superimposed and mutually spaced outer and innerwalls with said outer wall substantially gas-tight and said inner wallperforated, and said inner casing having superimposed and mutuallyspaced outer and inner perforated, Walls and a central substantiallygas-tight Wall interposed therebetween, said casings having an inletchamber at their exhaust-inlet ends with the latter and said chamberconstructed and arranged to interconnect the respective insides of saidcasings and to introduce the exhaust thereto, and said casings having anoutlet chamber at their exhaust-outlet ends with the latter and saidoutlet chamber constructed and arranged to interconnect their respectiveinsides and to carry the ex- 9 haust therefrom, said outlet chamberconnecting with means for at least slightly impeding the exhaust flowtherefrom, said means including a generally egg-shaped casing with agenerally tear drop shaped body mounted therein and spaced therefromwith itsv tail pointing baekwardly and projecting beyond the outlet endof the said egg-shaped casing.

EDDY D. LA'IULIPPE.

REFERENCES CITED Number Number 10 UNITED STATES PATENTS Name Date GrayApr. 1, 1919 Schnell June 23, 1931 Rauen Feb. 24, 1942 FOREIGN PATENTSCountry Date Great Britain Feb. 9, 1937 France June 2, 1939 Certificateof Correction Patent No. 2,543,461 February 27, 1951 EDDY D. LATULIPPEIt is hereby certified that error appears in the printed specificationof the above numbered patent requiring correction as follows:

Column 2, line 13, for the Words mulfler to read muyfler a; column 4:,line 23, for in read by; column 8, lines 11 and 59, for betwen readbetween; line 44:, same column, for substantialy read substantially;

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the case in the PatentOifice.

Signed and sealed this 1st day of May, A. D. 1951.

[SEAL] THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction Patent No. 2,548,461 February 27, 1951 EDDY D.LATULIPPE It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows Column 2, line 13, for the Words mufiier to read mufiler a;column 4, line 23, for in read by; column 8, lines 11 and 59, forIoetwen read between; line 44, same column, for substantialy readsubstantially;

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the case in the PatentOifice.

Signed and sealed this 1st day of May, A. D. 1951.

[SEAL] THOMAS F. MURPHY,

Assistant Oowz'ssz'oner of Patents.

